Siemens siprotec 7SA6 User Manual page 606

Installation and Commissioning
Directional
Comparison
Schemes
8-62
If the signal transmission path for the earth fault protection is the same path that was
already tested in conjunction with the distance protection according to Subsection
8.3.12.1, then this Subsection 8.3.12.2 is also of no consequence and may be omitted.
For the functional check of the earth fault protection signal transmission, the distance
protection should be disabled, to avoid interference of the tests by signals from the
distance protection: address  )&7 'LVWDQFH = 2)).
Prerequisites: 7HOHSURWHFWLRQ IRU (DUWK IDXOW RYHUFXUU 7HOHSURW
() in address  (Section 5.1) must be set to one of the comparison schemes
utilizing a release signal, i.e. 'LU&RPS3LFNXS or 8QEORFNLQJ; in addition the
setting in address  must be set to )&7 7HOHS () 21. Naturally, the
corresponding send and receive signals must be assigned to the corresponding binary
output and input. For the echo function, the echo signal must be assigned separately
to the transmit output.
For more information about the directional comparison schemes see Subsubsection
6.6.1.1 and 6.6.1.2.
A simple check of the signal transmission path from one line end is possible via the
echo function if these release techniques are used. The echo function must be
activated at both line ends i.e. address  must be set to )&7 :HDN ,QIHHG =
(&+2 RQO\; with the setting (&+2 DQG 75,3 a trip may result at the line end opposite
to the test location!
An earth fault is simulated in the direction of the line. This may be done with secondary
injection test equipment. As the device at the opposite line end does not pick up, the
echo function comes into effect there, and consequently a trip command is issued at
the line end being tested.
If no trip command appears, the signal transmission path must be checked again,
especially also the assignment of the echo signals to the transmit outputs.
This test must be carried out at both line ends, in the case of three terminal lines at
each end for each signal transmission path.
The functioning of the echo delay time and monitoring of the circuit breaker switching
status should also be tested at this time if this has not already been done under
8.3.12.1 (the operation of the protection at the opposite line end is checked):
The circuit breaker on the protected feeder must be opened, as must be the circuit
breaker at the opposite line end. A fault is again simulated as before. A receive signal
impulse delayed by somewhat more than twice the signal transmission time appears
via the echo function at the opposite line end, and the device issues a trip command.
The circuit breaker at the opposite line end is now closed (while the isolators remain
open). After simulation of the same fault, the receive and trip command appear again.
In this case however, they are additionally delayed by the echo delay time of the
device at the opposite line end (0,04 s presetting, address  7ULS(FKR '(/$<).
If the response of the echo delay is opposite to the sequence described here, the
operating mode of the corresponding binary input (H–active/L–active) at the opposite
line end must be rectified (see Sub-section 5.2.4).
The circuit breaker is opened again.
This test must also be carried out at both line ends, in the case of three terminal lines
at each line end and for each signal transmission path. Please take note of the last
margin heading "Important for All Schemes"!
7SA6 Manual
C53000-G1176-C133-1